1. Field of the Invention
The present invention relates to a combination weigher which includes weighing hoppers arranged in a linear shape and feeds to a packaging machine or the like products which have been weighed.
2. Description of the Related Art
Typically, products which have been weighed by a combination weigher are fed to, for example, a packaging machine, and are charged into packaging bags or packaging containers. Such a combination weigher which weighs the products is configured to include weighing hoppers arranged in a linear shape. Hereinafter, the combination weigher including the weighing hoppers arranged in a linear shape will be described.
In such a conventional combination weigher, for example, below the plurality of weighing hoppers arranged in a linear shape, a collecting chute is provided to gather the products which have been discharged from the weighing hoppers and to feed them to, for example, a feed inlet of a packaging machine. Each weighing hopper measures the weight of the products which have been fed thereto. For example, a controller performs combination calculation based on the measured values to determine one combination of weighing hoppers in which a total of the measured value falls within an allowable range with respect to a target combination weight and to determine it as a combination (hereinafter referred to as a “discharge combination”) for discharging the products. The weighing hoppers selected to form the discharge combination discharge the products. The discharged products slide down on the collecting chute and are fed into, for example, the feed inlet of the packaging machine.
Japanese Patent Application Publication No. Sho 58-161829 (hereinafter referred to as “document 1”) discloses a configuration in which a sorting device is disposed below a plurality of weighing hoppers arranged in a linear shape to route in two directions products which have been discharged from these plurality of weighing hoppers, a collecting chute is disposed below the sorting device to discharge the products in weighing hoppers selected to form a discharge combination, and a chute (hereinafter referred to as “defective product discharge chute A”) is disposed below the sorting device to discharge the products from, for example, a weighing hopper holding the products with an excess amount. In this case, the sorting device routes the products which have been discharged from the weighing hoppers to the collecting chute or to the defective product discharge chute A.
Japanese Utility Model Application Publication No. Hei. 3-123232 (hereinafter referred to as “document 2”) discloses that the products which are sent out from a supplying device are fed via linear feeders and others, a plurality of containers (hereinafter referred to as “weighing containers”) are arranged in a linear shape to measure the weights of the products, a collecting chute is disposed below these plurality of weighing containers to discharge to a packaging machine the products from the weighing containers selected to form a discharge combination, and a funnel-shaped chute (hereinafter referred to as “defective product discharge chute B”) is disposed below these plurality of weighing containers to discharge the products from, for example, a weighing container accommodating the products with an excess amount. In addition, this Utility Model discloses a configuration in which below a discharge outlet of the defective product discharge chute B, a belt conveyor is disposed to convey the products which have been discharged from the discharge outlet and to return them to a supplying device. In this case, the weighing containers are configured to be rotatable such that openings of the weighing containers face upward, downward, leftward, and rightward. With the openings facing upward, the products are fed to the weighing containers. For example, with the openings facing leftward and downward, the products are discharged onto the collecting chute, while with the openings facing rightward and downward, the products are discharged onto the defective product discharge chute B.
In the above described combination weigher, in the case of, for example, products which have a tendency to stick together, they sometimes stick together and are fed to the weighing hopper with a large amount at a time. For example, a weighing hopper which is fed with the products with an amount that is larger than an upper limit value of an allowable range with respect to a target combination weight, is not selected for the discharge combination. In a case where favorable combination weighing accuracy is obtained by setting the number of weighing hoppers selected to form the discharge combination to four in average, the operation is set so that the target feed amount for the weighing hopper is ¼ or substantially ¼ of the target combination weight. It is difficult to select for the discharge combination the weighing hopper which is fed with the products whose amount is significantly larger than the target feed amount, for example, twice as large as the target feed amount. This is because, if such a weighing hopper participates in a combination within a predetermined weight range, then the number of other weighing hoppers which can participate in the combination becomes smaller.
In a case where a package containing a predetermined number of products is manufactured, a combination of weighing hoppers in which a total weight of the products falls within the allowable range with respect to the target combination weight and a total number of the products is a predetermined number is determined as the discharge combination. In this case, when the products are fed to the weighing hopper with a large amount and the products whose number is larger than the predetermined number are fed to the weighing hopper as described above, this weighing hopper is not selected for the discharge combination. For example, in a case where favorable combination weighing accuracy is attained by setting the number of weighing hoppers selected to form the discharge combination to four in average and a package containing a smaller number, for example, seven pieces of products is manufactured, each weighing hopper must be configured to be fed with one to two pieces of products. For example, if a weighing hopper is fed with eight pieces of products, then the weighing hopper is not selected for the discharge combination.
If the weighing hopper which is fed with the products with an excess amount (hereinafter referred to as an “excess product weighing hopper”) as described above increases in number, then it becomes impossible to determine the discharge combination. Accordingly, to eliminate the excess product weighing hopper, the products must be discharged from the excess product weighing hopper.
In the configuration disclosed in the document 1, the products can be discharged from the excess product weighing hopper through the defective product discharge chute A. However, to weigh the products which have been discharged from the defective product discharge chute A again, an operator must return the products to the supplying device. In addition, the sorting device is not provided for each weighing hopper but is provided for all of the weighing hoppers. Therefore, when the products are discharged from the excess product weighing hopper, the weighing hopper selected to form the discharge combination must stop discharging for a moment, causing a reduced productive capacity.
In the configuration disclosed in the document 2, the products can be discharged from the weighing container (hereinafter referred to as “excess product weighing container”) holding the products with an excess amount through the defective product discharge chute B, and the belt conveyor conveys the products which have been discharged from the defective product discharge chute B and returns them to the supplying device. However, in a case where there are plural excess weighing containers at the same time, the products are discharged from the discharge outlet of the funnel-shaped defective product discharge chute B with a very large amount and are conveyed in a clumped state by the belt conveyor to be supplied to the supplying device. For this reason, in the case of the products which have a tendency to stick together, they might stick together on the supplying device and might be fed to again the weighing container with a large amount in a sticky state.
In the configuration disclosed in document 1, the sorting device is provided below the weighing hoppers, while in the configuration disclosed in document 2, the weighing containers are configured to be rotatable, to discharge the products selectively to the collecting chute or to the defective product discharge chute (A, B). However, in either case, the configuration for sorting the products is not easy.